Biotite

Biotit and Biotit lens
Biotite is black mica and takes its name from a physicist from France called Biot.
Biotite is monoclinic

Mineral class
formula:
K(Mg,Fe)3[(OH,F)2/AlSi3O10] + Ba,Cs,Li,Mn,Na,Sr,Ti K(Mg,Fe,Mn)3[(OH,F)2 / (Al,Fe)Si3O1 0] + Ba,Cs,Li,Na,Sr,Ti

Mohs hardness: 2.5 - 3
density: 3,02 - 3,12
Fissionability: excellent, elastically bendable split leaflets
Line colour: white
transparency: opaque to translucent

Healing Effects
Self-fulfilment, protection from foreign influences, helps to make decisions